Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Without any structured help beyond readOnlyHint=false and destructiveHint=false, the description discloses the approval guard, the exact approval_required error payload and how to retry with the token, value clamping behavior, that omitted fields retain their value, and that the response reports what now applies. It also frames the operation's blast radius (mail volume and paid finder spend) and dashboard parity. This is unusually rich behavioral disclosure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

It is front-loaded with the field semantics and scoping before the guard details, and every clause carries information. However, "Guarded" is used twice in adjacent sentences and the closing dashboard-parity sentence is closer to reassurance than instruction, so it is slightly inflated for its content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 10 all-optional parameters, no output schema and a non-trivial approval flow, the description covers the mechanics an agent needs: partial updates, mailbox vs project scope, clamping, and the approval round-trip. The return value is only described vaguely as "what now applies", which is the one gap for a tool whose success response matters.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 70%, and the description adds genuinely new meaning on top: partial-update semantics ("fields you leave out keep their value"), cross-parameter scoping (cap and reply reserve are mailbox-level, not project-level), and the fact that hour_from/hour_to/timezone/sending_days seed new campaigns. It does not explain the individual enum parameters or the per-field behavior of contact_checks_per_day, so it stops short of 5.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific resource and scope: sending limits and defaults, located as (App settings, Sending), covering the daily cap, reply reserve, window/timezone/days defaults, finder budget and contact checks. It also distinguishes mailbox-level fields from per-campaign defaults, which separates it from update_campaign_settings and update_project_settings. It never states the action as a clean verb first, so it lands just short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives clear routing context: the daily cap and reply reserve belong to the mailbox and therefore affect every project sending from it, while window, timezone and days are the defaults every new campaign starts with. That implicitly tells the agent when to use this rather than a campaign-scoped updater. No sibling tool is named explicitly as an alternative, so 4 rather than 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.